The preferred embodiments of the present invention relate to medical diagnostic X-ray imaging. In particular, the preferred embodiments of the present invention relate to dual energy decomposition for tissue specific imaging using a look-up table to obtain a range of cancellation parameters.
Today, doctors and technicians commonly have access to very sophisticated medical diagnostic X-ray imaging devices. Typically during the operation of an X-ray imaging device, an X-ray source emits X-ray photons under very controlled circumstances. The X-ray photons travel through a region of interest (ROI) of a patient under examination and impinge upon a detector. In the past, X-ray imaging devices employed rudimentary film based detectors. However, recent developments have led to solid state detectors comprised of a grid of discrete detector elements that individually respond to exposure by X-ray photons.
Regardless of the detector used, however, the goal remains the same, namely to produce a clear resultant image of preselected structures of interest (e.g., specific types of tissues) within the ROI.
There is an inherent difficulty associated with producing a clear resultant image, however. In particular, because the X-ray photons travel through the entire patient, the image formed on the detector is a superposition of all the anatomic structures through which X-ray photons pass, including the preselected structures of interest. The superposition of anatomic structures is sometimes referred to as “anatomic noise”. The effect of anatomic noise on the resultant image is to produce clutter, shadowing, and other obscuring effects that render the resultant image much less intelligible than the ideal clear resultant image.
Past attempts to reduce the effects of anatomic noise included, for example, “dual-energy” imaging. When employing dual-energy imaging, a doctor or technician acquired an image at high average X-ray photon energy, and an image at low average X-ray photon energy. Because different internal structures absorb different X-ray photon energies to different extents, it was possible to combine the two resultant images to suppress anatomic noise, according to:SB(x,y)=exp[log(H(x,y))−wlog(L(x,y))], (0<w<1)where SB is the decomposed image achieved through the log subtraction at a specific cancellation parameter w, H(x,y) is an image obtained at high energy, and L(x,y) is an image obtained at low energy. By varying w, SB becomes a decomposed image of either soft tissue or of bone.
However, in the past, users of the previously mentioned decomposition technique had to vary the cancellation parameter, w, manually through trial and error until the resultant image emphasized the soft tissue or bone of interest and de-emphasized the other. The resulting manual variation of the cancellation parameter in the log subtraction equation was time consuming and hindered the workflow in the clinical environment.
A need has long existed in the industry for a method and apparatus for dual energy decomposition that addresses the problems noted above and previously experienced.